Drop-on-demand inkjet printers eject ink drops from printhead nozzles in response to pressure pulses generated within the printhead by either piezoelectric inkjet ejectors or thermal transducer inkjet ejectors. The pressure pulses propel the ejected ink drops onto a recording medium to form an ink image. In a typical piezoelectric inkjet printer, a controller applies electric pulses, referred to as firing signals, to the piezoelectric inkjet ejectors to produce the pressure pulses, which eject liquid ink drops from the nozzles. The controller may electronically address each inkjet ejector individually to enable a firing signal to be generated and delivered for each inkjet ejector. The firing signal causes a piezoelectric device of the inkjet ejector receiving the firing signal to bend or deform a diaphragm and pressurize a volume of liquid ink in a chamber adjacent the diaphragm. Ink from a reservoir in the printhead refills the inkjet channels as the diaphragm returns to its rest position and produces a negative pressure that pulls ink into the inkjet ejector.
An inkjet printer may print images with numerous types of ink including phase change ink, gel ink, aqueous ink, and the like. Phase change ink, also referred to as solid ink, remains in the solid phase at an ambient temperature, which is the temperature of the air surrounding the printer. Accordingly, before the printhead may eject phase change ink onto the image receiving member, the printer heats the solid ink to produce liquid ink suitable for ejection. Gel ink remains in a gelatinous state at ambient temperature or changes to a gel state between the liquid and solid states. Before the printhead ejects gel ink, the printer heats the ink to impart a lower viscosity to the ink that is suitable for ejection. Aqueous ink remains in a liquid phase at ambient temperature and, therefore, the printhead may eject aqueous ink without heating the ink.
Some inkjet printers configured to print images with phase change ink include an image receiving member in the form of a rotating drum or belt coated with a layer of release agent. The printhead ejects drops of liquid ink onto the layer of release agent to form an image. Next, the printer transfers the ink image to a recording medium, such as paper. The transfer is generally conducted in a nip formed by the image receiving member and a pressure roller, which is also called a transfix or transfer roller. The printer may include a heater to heat the image receiving member and/or the recording medium prior to entry in the transfixing nip. As the printer transports a recording medium through the nip, the nip transfers the fully formed image from the image receiving member to the recording medium and concurrently fixes the image to the recording medium. This technique of using heat and pressure at a nip to transfer and fix an image to a recording medium passing through the nip is typically known as “transfixing,” a well known term in the art, particularly with phase change ink technology.
Some inkjet printers may undergo a warming period in which the printer heats one or more of the image receiving member, the ink, the transfix roller, and the recording medium to a respective operating temperature. During the warming period, the printer typically refrains from printing images until specific thermal operating design setpoints are reached. Of course, such restraint consumes energy resources without providing tangible output and increases the first print out time (FPOT), which is an important customer consideration. Reducing such periods of non-productive customer wait time is desirable.